Scarlett (Perdita Weeks) is an urban archeologist with multiple degrees, fluency in several languages, and a baffling supernatural hobby: getting her empiricism-loving science-hands all over that legendary alchemical prize, the Philosopher’s Stone. Determined to locate it in the deepest recesses of the Catacombs of Paris, she hits up her pal George (Ben Feldman) for help, along with a team of rogue cave-jumpers led by a messy-haired tagger named Papillon (Francois Civil). Off they go, into the pitch black.

Outside of the tourist-approved areas, tucked into unhappily cramped spaces, they meet a variety of creepy entities: a ringing telephone, a freaky nightgown choir whose repertoire consists of owwwwooooo noises, perfectly preserved corpses, a child ghost, a car on fire, and some guy. It’s the group’s very own haunted mansion, a hell upside-down populated with mirror images of their worst nightmares. Except Some Guy. Nobody knows what his deal is. He just stands around in the back of scenes being tall and unsettling.

Director John Erick Dowdle (who also co-wrote, alongside brother Drew Dowdle) knows the trauma of enclosed spaces, having also directed Quarantine and Devil, the one where everybody gets stuck in Satan’s elevator. And to his credit, there's an appropriately suffocating quality to scenes of cast members descending deeper and deeper into smaller and smaller death-tubes.

But something – actually, make that almost everything else -- gets lost along the way. Increasingly silly when it should become more and more terrifying, never once resorting to rational thought when goofy leaps of nonsense reasoning will play better, characters meet their ends before you know why you should care and puzzle pieces fall into place too late to retrieve your interest.

Adding insult to injury, sporadic arresting images drown in a chaotically edited blur of camera moves that actively lobby against visual understanding, the metaphysical weirdness serving as a half-hearted excuse for literal confusion. What should have been a wild mashup of The Descent and Raiders of The Lost Ark becomes the claustrophobia-making adult Goonies remake you never wanted, as scary as a trip to Carlsbad Caverns. Stay up top; there's almost nothing to see down here.

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